Objectives
Anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive rapidly progressive interstitial lung disease (RP-ILD) is a life-threatening disease, the aetiology of which remains unclear. To detect potential diagnostic markers, a transcriptome analysis of the lung sample from a patient with anti-MDA5 antibody-positive RP-ILD was performed.

Methods
RNA sequencing analyses of an autopsy lung sample from a 74-year-old woman with anti-MDA5 antibody-positive RP-ILD was performed and compared with an age- and sex-matched normal lung sample. Genes with changes of gene expression ≥5-fold were considered differentially expressed genes and analysed by Metascape. The levels of leukaemia inhibitory factor (LIF) were measured in the serum samples from 12 cases of anti-MDA5 antibody-positive ILD, 12 cases of anti-aminoacyl tRNA synthetase (ARS) antibody-positive ILD, 10 cases of anti-transcription intermediary factor 1γ/anti-Mi-2 antibody DM and 12 healthy volunteers.

Results
Gene ontology enrichment analysis on the RNA sequencing data showed a strong association with antigen binding. Upregulated expressions of IL-1β, IL-6 and LIF were also detected. Serum LIF levels were significantly elevated in anti-MDA5 antibody-positive ILD patients {median 32.4 pg/ml [interquartile range (IQR) 13.2–125.7]} when compared with anti-ARS antibody-positive ILD patients [4.9 pg/ml (IQR 3.1–19.7), P < 0.05] and DM patients [5.3 pg/ml (IQR 3.9–9.7), P < 0.05].

Conclusion
Our present study suggested that upregulation of LIF might be a new potential disease marker specific for anti-MDA5 antibody-positive ILD.

1. Naoko Okiyama,Professor
   
   Department of Dermatology, 
   Graduate School of Medical and Dental Sciences,
   Tokyo Medical and Dental University(TMDU)
   E-mail：okiy.derm(at)tmd.ac.jp
   
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